I was asked today to do a short tutorial on a little known yet valuable command in Rhino called Fin.
Fin, according to the help manual, “Creates a surface by extruding a curve on a surface, normal to the surface.” The practical example below will use the fin command to create stair a simple staircase based on bent geometry.
Problem: This technique will not work with an applied UV curve nor geometry which has been oriented to a predefined surface; in both instances the threads on the staircase become skewed. When offsetting a polyline which has been through bend, etc. the offset will not be fully realized, so offset/loft wont work either.
Also note that this is not for wild, topological stairs (which may or may never be used/built/whatever), but is for using very controlled geometries to create stairs which someone on a cane might use.
1. Create staircase geometry (lines). JOIN them all together as one line.
2. Manipulate by the ROTATE/BEND/TWIST commands to desired state.
3. Use interpolated curves along the top edge of the stairs, so that the curve your creating follows the curve of staircase. Copy this new curve vertically above and below the stair geometry. Connect these two new lines with single straight line. SWEEP2 the two curves and the straight line to create a surface parallel but larger than the new staircase geometry.
4. FIN the staircase curved polyline. Select the surface created in step 3 as the surface as the “base surface.”
5. Erase/Delete the construction curves and surfaces to complete staircase.
Also know that you can build stairs using Grasshopper, if that’s your thing.
Leave questions in the comments-